Field of the Invention
This invention relates to a floating structure from which drilling or production operations are carried out. It relates especially to the installation of Vertically Moored Platforms in deep water.
In recent years, there has been considerable attention attracted to the drilling and production of wells located in water. Wells may be drilled in the ocean floor from either fixed platforms in relatively shallow water or from floating structure or vessels in deeper water. The most common means of anchoring fixed platforms includes the driving or otherwise anchoring of long piles in the ocean floor. Such piles extend above the surface of the water and support a platform attached to the top of the piles. This works fairly well in shallow water, but, as the water gets deeper, the problems of design and accompanying costs become prohibitive. In deeper water, it is common practice to drill from a floating structure.
In recent years, there has been some attention directed toward many different kinds of floating structures. One system receiving attention for mooring is the so-called Vertically Moored Platform. Such a platform is described in U.S. Pat. No. 3,648,638, issued Mar. 14, 1972, Kenneth A. Blenkarn, inventor. Key features of the disclosure in that patent are that the floating platform is connected to an anchor only by elongated parallel members and the floating structure has buoyancy means designed especially with respect to the trough of a design wave so as to minimize mooring forces imposed on the vertically elongated members which anchor the structure, such as those forces which may be caused by passing waves.
Pertinent prior art includes the aforesaid patent 3,648,638 and U.S. Pat. No. 3,976,021, issued Aug. 24, 1976, Kenneth A. Blenkarn and William D. Greenfield, inventors. However, the riser pipe/jacket vertical bearing described herein was not described in said patent 3,648,638. Further, it was not claimed in said patent 3,976,021, although described.